1. Field of the Invention
The present invention relates to the field of memory chips.
2. Discussion of Related Art
A known integrated memory IC 100 that is a writeable memory of the DRAM type is shown in FIG. 1. Such a dynamic random access memory (DRAM) chip 100 includes a plurality of memory storage cells 102 in which each cell 102 has a transistor 104 and an intrinsic capacitor 106. As shown in FIGS. 2 and 3, the memory storage cells 102 are arranged in arrays 108, wherein memory storage cells 102 in each array 108 are interconnected to one another via columns of conductors 110 and rows of conductors 112. The transistors 104 are used to charge and discharge the capacitors 106 to certain voltage levels. The capacitors 106 then store the voltages as binary bits, 1 or 0, representative of the voltage levels. The binary 1 is referred to as a “high” and the binary 0 is referred to as a “low.” The voltage value of the information stored in the capacitor 106 of a memory storage cell 102 is called the logic state of the memory storage cell 102.
As shown in FIGS. 1 and 2, the memory chip 100 includes six address input contact pins A0, A1, A2, A3, A4, A5 along its edges that are used for both the row and column addresses of the memory storage cells 102. The row address strobe (RAS) input pin receives a signal RAS that clocks the address present on the DRAM address pins A0 to A5 into the row address latches 114. Similarly, a column address strobe (CAS) input pin receives a signal CAS that clocks the address present on the DRAM address pins A0 to A5 into the column address latches 116. The memory chip 100 has data pin Din that receives data and data pin Dout that sends data out of the memory chip 100. The modes of operation of the memory chip 100, such as Read, Write and Refresh, are well known and so there is no need to discuss them for the purpose of describing the present invention.
A variation of a DRAM chip is shown in FIGS. 5 and 6. In particular, by adding a synchronous interface between the basic core DRAM operation/circuitry of a second generation DRAM and the control coming from off-chip a synchronous dynamic random access memory (SDRAM) chip 200 is formed. The SDRAM chip 200 includes a bank of memory arrays 208 wherein each array 208 includes memory storage cells 210 interconnected to one another via columns and rows of conductors.
As shown in FIGS. 5 and 6, the memory chip 200 includes twelve address input contact pins A0-A11 that are used for both the row and column addresses of the memory storage cells of the bank of memory arrays 208. The row address strobe (RAS) input pin receives a signal RAS that clocks the address present on the DRAM address pins A0 to A11 into the bank of row address latches 214. Similarly, a column address strobe (CAS) input pin receives a signal CAS that clocks the address present on the DRAM address pins A0 to A11 into the bank of column address latches 216. The memory chip 200 has data input/output pins DQ0-15 that receive and send input signals and output signals. The input signals are relayed from the pins DQ0-15 to a data input register 218 and then to a DQM processing component 220 that includes DQM mask logic and write drivers for storing the input data in the bank of memory arrays 208. The output signals are received from a data output register 222 that received the signals from the DQM processing component 220 that includes read data latches for reading the output data out of the bank of memory arrays 208. The modes of operation of the memory chip 200, such as Read, Write and Refresh, are well known and so there is no need to discuss them for the purpose of describing the present invention.
It is noted that new generations of SDRAM chips are being optimized for bandwidth. The most common method of accomplishing such optimization is to increase the clocking rate of SDRAM chips. By increasing the clocking rate and shortening operation cycles for normal operations, the consumption of current and power during operations increases. Since the internal temperature of the chip is proportional to the power consumption, increasing the clocking rate will result in an increase in the internal temperature of the chip.
It is known that there are circumstances where the heat generated in SDRAM chips optimized for bandwidth exceeds the maximum amount of heat that the chip package can dissipate. In most cases, the extent of time at which the generated heat exceeds the maximum amount of heat that can be dissipated is so short that the thermal constant of the chip package is sufficiently high in value so as to prevent destruction of the SDRAM chip. However, when such SDRAM chips are controlled by software, it is possible to write a command pattern, such as a thermal virus, which requests optimizing bandwidth and increasing clocking for sufficiently long periods of time that the thermal constant of the chip package is not sufficiently high to prevent the thermal destruction of the SDRAM.